Van Allen Belts The problem of protecting astronauts against the radiation found within the Van Allen belts was recognized before the advent of manned space flight. These two bands of trapped radiation, discovered during the Explorer I flight in 1958, consist principally of protons and high-energy electrons, a significant part of which were, at that time, debris from high-altitude tests of nuclear weapons. The simple solution to protection is to remain under the belts [below an altitude of approximately 556 km (? 300 nautical miles)] when in Earth orbit, and to traverse the belts rapidly on the way to outer space. In reality, the problem is somewhat more complex. The radiation belts vary in altitude over various parts of the Earth and are absent over the north and south magnetic poles. A particularly significant portion of the Van Allen belts is a region known as the South Atlantic anomaly (figure 1). Over the South Atlantic region, the geomagnetic field draws particles closer to the Earth than in other regions of the globe. The orbit inclination of a spacecraft determines the number of passes made per day through this region and, thus, the radiation dose. Particles within the Van Allen belts, in spiraling around the Earth’s magnetic lines of force, display directionality. This directionality varies continuously in angular relationship to the trajectory of the spacecraft. Therefore, dosimetry instrumentation for use in the Van Allen belts had relatively omnidirectional radiation sensors so that the radiation flux would be measured accurately. The Van Allen belt dosimeter (figure 2) was designed specifically for Apollo dosimetry within these radiation belts. Radiation doses measured during Apollo were significantly lower than the yearly average of 5 rem

set by the U.S. Atomic Energy Commission for workers who use radioactive materials in factories and institutions across the United States. Thus, radiation was not an operational problem during the Apollo Program. Doses received by the crewmen of Apollo missions 7 through 17 were small because no major solar-particle events occurred during those missions. One small event was detected by a radiation sensor outside the Apollo 12 spacecraft, but no increase in radiation dose to the crewmen inside the spacecraft was detected.

Originally posted by DJW001
Finally! So exactly how much radiation would astronauts be exposed to during a two week trip to the Moon?

The Apollo astronauts traveled through the Van Allen radiation belts on the way to the Moon; however, exposure was minimized by following a trajectory along the edge of the belts that avoided the strongest areas of radiation. The total radiation exposure to astronauts was estimated to be much less than the 5 rem set by the U.S. Atomic Energy Commission for people who work with radioactivity.

The National Council on Radiation Protection (NCRP) says that the average resident of the U.S. receives about 360 mrem every year from background sources. This comes from outer space, radioactive materials in the earth, and small amounts of radioactive material in most foods we consume.

In fact, you receive about 2 mrem per year from sleeping next to someone! This is because all of us have very small amounts of naturally occurring radioactive materials in our bodies.